The present invention relates to a look-up table device and an image generation device that uses the same.
A look-up table device that is known in the art receives a digital input value and uses a given table to output a digital output value.
An example of such a look-up table device is described below. This look-up table device uses memory that is provided with an n-bit address bus and a k-bit data bus, where the address bus is used as an input signal line and the data bus is used as an output signal line. With a look-up table device of this format, the table has a form such that each of k-bit digital output values is stored in each of 2n storage areas which correspond to. n-bit digital input values. In other words, the look-up table device of this type must have a storage capacity of at least 2nxc3x97k-bit of memory.
If either n or k is large, therefore, the table itself will become large, leading to a problem concerning an increase in the necessary storage capacity therefor. Particularly if n is large, the necessary storage capacity will increase exponentially in correspondence with 2n. There is therefore a demand for a look-up table device that can reduce the necessary storage capacity to a minimum, even in such a case. In addition, when the necessary storage capacity increases in this configuration, the time taken to overwrite the values in the table also increases. This raises another problem in that this device is unsuitable for applications where rapid overwriting of table values is necessary.
There is thus a further demand for a look-up table device that enables various different conversions, with few table values.
The present invention was devised in the light of the above technical problems and has as an objective thereof the provision of a look-up table device that makes it possible to implement various conversions within a limited storage capacity, and an image generation device that uses that look-up table device.
To solve the above described technical problems, the present invention provides a look-up table device for converting a digital input value into a digital output value, comprising:
section deriving means for receiving the digital input value, deriving the section to which the digital input value belongs, and outputting section information that is specifies the section;
computation parameter output means for receiving the section information and outputting a computation parameter corresponding to the section information; and
computation means for receiving the digital input value and the computation parameter, performing a given computation based on the digital input value and the computation parameter, and outputting the result of the computation as the digital output value.
With this aspect of the invention, the section deriving means first derives section information such as the number of a section to which the digital input value belongs, then the computation parameter output means outputs a computation parameter based on this section information. The computation means then performs a given computation based on the digital input value and the computation parameter, to obtain the digital output value.
With this aspect of the invention, it is not necessary to provide the same number of digital output values to match all of the digital input value. This means that it is possible to greatly reduce the necessary storage capacity, in comparison with a conventional look-up table device. Moreover, the device of the present invention is advantageous in that it makes it possible to implement various different types of conversion, by setting different combinations of computation parameters and given computations.
In a second aspect of the present invention, the section deriving means comprises means for storing delimiter information of sections classifying the digital input value, and derives the section to which the digital input value belongs based on the delimiter information. The way of delimiting sections can be varied in various ways by providing such storage means and modifying the contents stored in this storage means as appropriate. AS a result, it is possible to obtain any of various input-output digital value conversion characteristics that the user desires. Note that the delimiter information in this case is not restricted to delimiter values for the sections; various other values such as the central values of the sections could equally well be used instead.
In a third aspect of the present invention, the computation parameter output means comprises means for storing a computation parameter corresponding to each of the section information, and reads out the computation parameters from the storage means based on the section information. The values of computation parameters to be used in the given computation can be modified in various ways by providing such storage means and modifying the contents stored in this storage means as appropriate. As a result, it is possible to obtain any of various input-output digital value conversion characteristics that the user desires.
In a fourth aspect of the present invention, the computation means obtains a difference value between the digital input value and a delimiter value that is specified by delimiter information of the section to which the digital input value belongs, and performs the given computation based on the difference value and the computation parameter. Performing the computation based on such a difference value makes it easy to obtain a conversion characteristic with no discontinuities. This aspect also has the advantage of making it possible to utilize the delimiter value used by the section deriving means, as a base value for obtaining the difference value.
In a fifth aspect of the present invention, the computation parameter output means outputs the coefficients am to a0 of the expression mXm+amxe2x88x921Xmxe2x88x921+. . . a1X+a0 in m (where m is greater than or equal to 1) degree expression, as the computation parameters; and the computation means obtains amXm+amxe2x88x921Xmxe2x88x921+ . . . a1X+a0, based on X that is specified by the digital input value and am to a0 that are included within the computation parameters, and outputs the obtained result as the digital output value. Performing the given computation based on a linear computation equation in this manner makes it possible to simplify the hardware configuration of the computation means.
A sixth aspect of the present invention relates to a device comprising at least one of a gamma compensation means that performs gamma compensation by using the above look-up table device, and a depth cueing means that performs depth cueing by using the above look-up table device; and means for generating an image to which at least one of the gamma compensation and the depth cueing has been applied. By using the look-up table device of the present invention for the conversion of gamma compensation or depth cueing in this manner, not only is it possible to provide any user-desired conversion processing, it is also possible to reduce the size of the hardware that performs such conversion.